Cytokeratin and vimentin heterogeneity in human cornea

The body of information on cytokeratin expression in non-epithelial and epithelioid cells is steadily increasing. In this immunocytochemical study using a panel of monoclonal cytokeratin antibodies, we regularly observed cytokeratins no. 8 and 18 together with vimentin in the corneal endothelium of the human eye, but the antibodies exhibited a heterogeneous reactivity pattern. In fetal eye specimens, cytokeratins were already present at the 10th week of gestation, and disappeared at about the 22th week of fetal development. Corneal and conjunctival epithelial cells in the same specimens usually showed uniform cytokeratin 8 and 18 expression, beside the well documented presence of corneal and squamous epithelium type cytokeratins. In 2 of our 7 cases of adults, cells coexpressing cytokeratin and vimentin were observed in the corneal epithelium. The data provide another example of modulation of cytokeratin and vimentin expression, in which simplistic rules cannot be applied.